Well survey method and apparatus



Jan. 30, 1945. R. E. FEARON 2,368,532

WELL SURVEY-METHOD AND APPARATUS Filed Dec. 27. 1939 Patented Jan. 30, 1945 Well Surveys, Incorporated, Tulsa, Oklam ga corporation of Delaware v Application December 27, 1939,"Serial No. 311,219

11 claims. '(clgzsog-ss) This` invention relates to the art of geophysical prospecting and particularlyto the measur ing of the characteristics of the geological formations that surround, at various levels, drill holes or otherk deep, narrow openings in the ground.

Especially is this invention concerned with a method and means whereby power may be transmitted to the measuring instrument in the hole and the results of the measurement returned to the surface to a recorder located there.

Previous to this invention it has been necessary either to lower into the hole with the measuring instrument all of the power supplying equipment necessarytov operate the instrument and all of the recording equipment necessary to record its findings or provide numerous heavily `insulated conductors` extending Vfrom the instrument in the hole to the surface of the ground. The provision-of a multi-conductor cable sufficiently well insulated and armored to withstand the eXtremely high pressures and the rough mechanical usage encountered, and at the same time preserve the conductors in a high state of insulation, has been a very serious problem in this field. Great lengths oi cable must be lowered into a well in order to reach the levels it is desired to exploreand it is extremely difficult to make a cable that will withstand thev pressures and the fluids encountered at these levels.-

Batteries can be lowered with the instrument to provide a source of power but it is diicult to provide a satisfactory recorder and arrange it in such a way that it can be lowered with the instrument anda record obtained of the measurements satisfactorily correlated with indications ofthe depths at which theywere taken. Even the lowering of batteries with the instrument is unsatisfactory becauseit eliminates any outside control of the instrument and makes the instrument quite heavy and hard to handle. Fur- Y ther, the larger the instrument and its accessories, the larger must be the casing or capsule which contains it and this engenders mechanical difficulties including trouble inr sealing the instrument tightly against the high pressure fiuids that will be encountered and diflicultiesin rais'-y ring and lowering the capsule in thev well.

'V In its Ipreferred form, the present inventionl is of. in the well.

a device lfor measuring, by the use ofl an ioniza-` `tioncl'iamberI the' radioactivity encountered at various levels in a drill hole and includes inthe y capsule or casing'with the measuring instrument all of the mechanism necessary to make anull type of measurment of the intensity of the radiations except for the power supply and the recorder. These are located on the surface instead In rorder to get the main supply of power to theudevice an alternating current power source is connected to the cable which supports the capsule` inthe well on one side and grounded Y, on theother. At its lower end-this cable is' connected through a suitable filter which passes only currentl of ythe right frequency and through a power pack arrangement such as is commonly used in radios,` to the units which must `be powered.

The only place where power is needed that is not supplied fromthis main power pack is a resistor across whichma voltage drop is developed to balance that caused in a primary resistor by the rlowof the ionization chamber current. lThe current for this balancing yresistor-is sent from the surface through the samewireas the main operating power by passing it rst to avery low frequency filter that will allow the balancing current topass but will not allow currents of higher frequency to pass, then through a band elimination vfilter which specifically prevents entry into thev balancing current supply system of the current of the frequency used in the main power supply, and then into the supporting line. At the .chamber or capsule the resistor current is taken from the main line through a band elim- I ination lter which blocks out ,the currentof the main p ower supply, passed through a lter which blocksall but very low frenquencies and finally applied to the balancing resistor. i

Any voltage difference between the voltages of the primary and balancing resistors is applied to a communtator or interruptor drivenfrom'the power pack and the interrupted current is then passed tov an amplier also poweredfrom the power pack and finally to a generator of carrier wavesvwhere it serves to k[modulate thecarrier waves, preferably by a frequency type of modulation so that attenuation will not affect the accurate transmission Aof the indication. carrier wave generator is also powered from the power pack;

' The modulated carrier wave passes throughA a transformer andaband pass filter, which passes only waves of a frequency approximately that of the carrier, to the band elimination nlter which blocks out the current intended for the power pack and through this filter linto the main supporting cable. At the upper end of the shaft this modulated carrier current passes through the band elimination lter at that end, which has already been mentioned as blocking the main power current out of the remainderof the circuit, from this filter through a band pass filter similar to the one in the capsule, to an amplifier and finally to one coil of a double coil galvanometer or dynamometer.

The commutator in the 4capsule also-arranged so as to produce at the same time a second current, which current is of relativelyconstant amplitude but of a frequency indicative of the frequency of operation of the commutator. This current passes through a transformer, a band pass lter passing only that general frequency and the band elimination filter, which blocks out the power current, into the main line. At the upper end of the line this same current, which may be called a phasing current, passes through the band elimination filter at that end and through its particular band pass filter and to the other coil of the galvanometer or dynamometer. With the two currents mentioned acting on the dynamometer there is immediately an indication of the existence and direction of any unbalance between the primary resistor and the balancing resistor in the well and this difference can be adjusted to zero by adjusting the amount of current that is sent down to the balancing resistor. The current sent to the balancing resistor is then a measure of the intensity of the radiations in the well'. All of this balancing can be automatically controlled at the upper end of the well by a device known as a Micromax which device is described in U. S. patents, Nos. 1,578,279; 1,934,882; and 1,935,732.

In order 'that a better understanding may be had of the details of the preferred form ofthe device constructed according to the principles of this invention, such a device isyshown in detail in .the accompanying drawing and-described in detail hereafter. However, itis to be understood that the principles of this invention may" be applied to the making of measurements other than those of radioactivity and by systems'other than a "null system such as here described.

In the drawing the device illustrated is one which is particularly useful for the purpose of exploring oil wells to determine the radioactivity of the formations surrounding the welll at various levels. Those circuit elements shown inthe lower part of the drawing are all contained within the chamber -or capsule which is lowered into the well while all of the remaining elements, those shown at the top of the drawing, are located on the surface of the ground.

In operation, altem-ating current is supplied from a source I to ground and to the cable 2 which supports the capsule in the well. This current is preferablyat around 800 cycles frequency and around 60 volts potential. When this cul`- rent reaches the capsule it is taken from the supporting cable and from ground and passed through a band pass lter 3 which passes only current of around 800 cycles. From the band pass filter it goes through a coupling transformer 4 and to avpower pack 5. This'power pack supplies powerto a number of circuit elements which will later be described.

` potential applied across the elements of the ionization chamber a current flows in the chamber proportional to the intensity of the radioactive radiations that irnpinge upon it. This current in turn developes a voltage drop across the resistor 6 also proportional to the :intensity of the radiations.

In series with the resistance B is a balancing .resistor 9 which, when supplied with the proper amount of current, will have a voltage drop exactly balancing the one across the primary resistor '6. In order to supply this current to the balancing resistor 9 an adjustable source of current is provided at the surface. This is shown in the drawing as a battery Ill with a potentiometer II connected thereacross and an ammeter I2 in series therewith.

Current from this system is passed through a low pass filter I3 which will pass only a steady or very low frequency current, for example, 3 cycles or less and from this lter to ground and through a band elimination filter I4 to the main supporting cable 2. The band velirninationiilter is designed specifically to eliminate currents of the frequency used for the main rpower supply, in the present case, current of Aaround 800 cycles frequency.

As the balancing current reaches the capsule or container in the well it` is taken from the `supporting line through a band elimination -filter I5 similar to the one at the surface, namely one which blocks out the 800 cycles current used for the power supply and then through a low pass lter vII which will pass only a steady or 'very low frequency alternating current to the balancing resistor 5. Decoupling resistors I1 are placed across the output of the low pass filter I6 and in series with the balancing resistor 9 to effect a general decoupling of the balancing resistor 9 from the remainder of the circuit.

Connected in series with the two resistancesA 6 and Sis a commutator or periodic interrupter Q18 driven from the power pack and operating to produce two pulsating currents, one of relatively steady amplitude .and with a frequency ycorresponding tothe speed of the commutatorand the other with the same frequency but with an amplitude depending upon the potential diierf ence, if any, between `the primary and balancing resistors yli and 9.

The constant amplitude current is passed through a transformer .I9 to a band pass lter 20 which passes only currents of approximately the frequency that will be generated by the commutator, in the :present case about 70 cycles.` From this filter the current passes on one side to the ground and .the other side through the band elimination lter I5 which blocks out'the power supply current, then through the main supporting cable 2 to the surface where it again passes through a band elimination filter I4, already mentioned, which blocks out the 800 cycle power supply current, then through a band pass lter 2l which passes only current of around 70 cycles and finally to one of the coils of a double coiled galvanometer or dynamometer 22.

The pulsating current from the commutator I8 that corresponds in amplitude to any difference in potential between the two resistors is passedto an amplifier 23v and then to an oscillator 24 when it acts to modulate an alternating current generated thereto and of a frequency such that it about 245 cycles.

-will actas a5carrier. wave. Fromthe yoscillator 24 the modulated carrier ywave is passed through a coupling ktransformer, 25 to a band pass lter 26 which will pass only alternating currents with a frequency in the neighborhood wave frequency. After passing through this filgj ,ter the current is amplified by an amplifier 28, demodulated by a demodulator 2 9 and passed -to the other coil of the dynamometer or galvanometer 22. i y,

With the lcircuit 'in operation and in balance there will be no voltage difference resulting from the combination of the primary resistor 6 and the balancing resistor 9 and hence no current through the amplier 23 and none from the demodulator 29 to the'dynamometer or galvanometer. ,Under these circumstances one of the coils will be dead and there will be no movement in the dynamometer or galvanometer 22 and the needle will merely rest in the neutral position. However, if the intensity of the radiations impinging upon lthe ionization chamber change then the vcurrent ilow in the primary resistor 6 will also change and a state of difference between the voltages across the i y.a

be madewithout departing from the spirit'of this invention. For example, the frequencies 'used may be.v rearranged to suit f particular circumstances, other characteristics than radioactivity maybe measured, a direct recording system may be substitutedfor the null system, or the null system may be used without converting the indications into pulsating currents.

I claim:

Y 1.In a device for geophysical exploration in which an instrument is lowered into an Opening vin vthel earthr to f. measure characteristics of thev surrounding strata and' a record-er is positioned at. the surface tov record the measurements, the

improvement which comprises as means to conneet the measuring instrument with the recorder and'wi'that least one source of power also positionedv on the surface, Aa cable connected to the ymeasuring instrument andv extending to the surprimary and lbalancing resistors 6 and 9 will temy porarily exist. Thischange may be either in one direction or the other depending upon whether vthe intensity of the radiations impinging upon the l ionization chamber increase or decrease. In any.

event a current representing the diierence will be transmitted to the amplier 23 through the commutator I8 and its phase relation to the con# stant amplitude pulsating current produced by thecommutator, will depend upon the direction @ofthe potential difference between the resistors.

"After passing through their respective vcircuits the constant amplitude alternating vcurrent and ythe alternating current representing the differ-v ence in potential will come together in the double coiled galvanometer or dynamometer. At this time the direction of the deflection will ,depend upon the phase relation of the two currents and Ihence a deection in one direction will indicate ,a greater voltage drop across the'balancingresistor than across the primary resistor and a delilecti'on in the other direction will indicate the f reverse condition. With this indicationas aguide the potentiometer Il may be adjusted to. send I more or less current through the balancing -resistor 9 and thus brin-g the system back into balance. The new setting of the potentiometer Il and the amperage indicated by the ammeter: l2

will then indicate the intensity of the radiations. The record of the measurements, in `actual practice, will ordinarily be made automatically andthe recorder will usually be driven by an electrical transmission from the cable as it enters and leaves the well so as to correlate the determinations with the depth at which they are made. The

Micromax recorder already mentioned has been y' found satisfactory for performing the vrecording function and may be driven by a fSelsyn electricaltransmission system which drives it at a f speed proportional to the speed at which the sup- ,DOrting cable enters or leaves the drill hole. n

purer, detaiied changes iny thesystemfmay also :face to support the measuring yinstrument, and

form an electrical connection thereto, a source of electrical'current connected to said cable and the ground at the upper end of the cable, means at the measuring device connected between the ground andthe lower end of the cable for receiving said current and utilizing it as power to operate the measuring device, means at the measuring device for impressing upon the surrounding earth and the supporting cable through filters that will exclude the main power supply current and each-other, at least two alternating elec -trical currents of different frequencies, the phase relation and relative magnitude of certain components of. said alternating currents being indicative of the state of said measuring instrument, means at the surface end of the cable for removing said indicating currents through similar .ilters andtmeans for recording the ymeasurement made by the instrument as indicated by the said indicatingvcurren'ts. y

2.-In a deviceffor geophysical exploration in f which an instrument is lowered into an opening inthe earth to measure characteristicsof the surrounding strata and a recorder is positioned at the surface to record the measurements, the improvement which comprises as means to conneet the measuring instrument with the recorder and with a source of power also positioned on the surface, a cable connected to the measuring instrument and extending to the surface to support the measuring instrument and form an electrical connectionv thereto; a `source of electrical current connected to said cable and the ground at the upper end of the cable, means at the measuring device connected between the ground and the lower end of the cable for receiving said current and utilizing it as power to operate the `measuring device, means also at the upper end of the. cable for supplying .a balancing current to bring the measuring vdevice to a state of" balance during each measurement, said means being connected to the cable and ground at the upper end of the cable, through a filter that willexclude they main power supply current andother unwanted currents, means at the measuring instrument for removing said balancing current from said cable and ground vand applying it to said measuring device, said means including a similar filter, .means at the measuring device for impressingupon the cable andground at least two alternating electrical currents of'different frequencies, the phase relation and relative ymagnitudefof certain components of said alternating currents beingindicative of the state of ,balance 'at the surface to record the measurements, the

improvement which comprises as means'to connect the measuring :instrument with the rec order and with a source of power also posi- .tioned on the surface, a :cable: 'connected'to the measuringinstrument and extending ftothe surface to support the measuring instrument and form an electrical connection thereto', a -source of electrical current connected to said cable fand the ground at the Vupper end of `the cable, means at the measuring device connected between the ground and the lower end 'of the 'cable for receiving said current and utilizing it as lpowerito `operate the measuring device, means also at the upper end of the cable for :supplying a 'balancing current .to bring vthe measuring device v.to Va state of balance during each measurement,

said means being lconnected to .the cable and groundat the upper vend of lthe cable, through a rllter'that will exclude the :malin power supply current and other 'unwanted currents, means at the measuring instrument "for -removing .said balancing current from said cable and .ground and applying it to said `measuring device, said means including a similar filter, means .at the measuring device for impressing upon the cable and ground atleast two alternatingelectrical currents of cliierent frequencies, fthefphase relation and relative magnitude lof certain lcomponents of said alternating currents fbeing 'indicative of the state of balance of said measuringdevice, means at the surface -end of th'e cable for removing said vindicating currents through similar lters, means for comparing said components, means for adjusting the balancing current by reference to said comparison to bring the instrument to a state of balance, means -to record the' amount of current necessary to establish balance and means 'operated in laccordance with the movement of said cable to lcorrelate the record of current with a record of the depth at which the measuring instrument is operating.

4. In a device for geophysical exploration in which an instrument is lowered into an opening in the earth to measure characteristics ofthe surrounding strata and a recorder `isposi-'fioned at the surface to record the measurementsy the improvement which comprises as 'means to connect the measuring instrument with the 'recorder and at least one Asource Aof power also positioned on the surface, a cable connected to the measuring instrument and extending to Ithe surface to support the measuring instrument and form an electrical connection thereto, a source of alternating electrical current connected to said cable and the ground atthe upper end of the cable, means at the measuring device connected between the ground and the lower end of the cable for receiving said cur-rent and utilizing it as power to operate the measuring device, means at the measuring device for impressing upon 'the surroimding earth andthe :casacca supporting cable -through filters that will exclude the main power supply current and leach other', at least .two alternating electrical currents of .frequencies 'different 'from eachother and different .from that of the vpower supply, one of said .currents :being modulated and the other 'being constant so that the Aphase relation and relative -magnitude of certain components of said limpressed alternating currents being indicative of the state of said measuring instrument, means .at the surface end of the 'cable for removing said indicating currents through similar filters :and means for recording the indicated measurement.

:5. In `a device for geophysical exploration in which an instrument comprising an ionization kchamber in series'with a primary fixed `resistance is lowered into an opening in 'the earth to measure characteristics of the surrounding strata anda recorder is positioned at the surface to record the measurements, the improve- -ment which comprises as ,means to connect 'themeasuring instrument with the recorder fand with a sour-ce of power also positioned on 'the surface, `a, cable Aconnected to the measuring instrument and extending to the-surface to support the measuring instrument Iand -iorm an electrical connection thereto, a source :of electrical current connected to said cable and the ground at the upper end of the cable, means at the measuring device connected between the ground and the lower end of the cable for receiving said current and converting it into power '-to operate the measuring device including, primarily, a, constant electrical potential for said said ionization chamber circuit, means also at they upper end of 'the cable for supplying a balancing current to bring the measuring device to a state of balance during each measurement, said means being connected to the cable and ground at the upper end of the cable through a -iilter that will exclude the' main power supply current and other unwanted currents, means at the measuring instrument including a similar iilter, for removing said balancing current `from said cable and ground and applying it to a ballancing ,resistor connected at one end to the resistor in the ionization chamber circuit so that the voltage developed across the two resistors will be the diierence between the Voltage developed by the ionization chamber current in the primary resistor and that `developed -by the balancing current in the balancing resistor,com

mutator means driven by current from the 4power supply means for generating a constant ampliy tude, constant frequency `alternating `phasing current and at the same time yconverting any voltage diierence developed across the balancing and Aprimary resistors into an altertnating indicating current of the same frequency :as the phasing current but with an l'amplitude and phase relation to the phasing current that de- -pends 'upon the magnitude and direction of said voltage difference, means at the lmeasuring device powered by said 'power supply means for impressing upon thev cable and ground one fof said alternating currents, said means including -a lter which lexcludes currents of other ireyquencies,.means powered by `said lpower supply means for generating and impressing on the.

ground and cable acarr'ier current of a diierent frequency from vsaid alternating currents but modulated by the other alternating current, said 'means including a filter which excludes `fremoving and separating the phasing and indicat-` ing currents through filters similar to these through which they entered the cable, means for comparing said phasing and indicating currents, means for adjustingthe balancing current lby reference to said comparison to 1bring the instrument to a state of balance and meansY to record the amount of current necessary to establish balance. o

6. In a device for geophysical exploration in which an instrument is lowered into an opening in the earth to measure characteristics ofk ,surrounding strata and a recorder is positioned at the surface to record the measurements, the im.

provenient which comprises as means to connect" the measuring instrument with the recorder and-I with at least one source of power also positioned on the surface, a cable connected to the measuring instrument and extending to the surface to support the measuring instrument and form an electrical connection thereto, a source of Velectrical current connected to said cable andthe ground at theupper end of the cable, means aty the measuring device connected between the ground and the lower end of the cable for receiving said current and utilizing it as, power to operate the measuring device, means at the measuring device for impressing upon the surrounding earth and the supporting cable at least two alternating electrical currents of diierent.` frequencies, the phase relation and relative magnitude of certain components of said alternating currents being indicative of the state of said measuring instrument, means at the surface end of the cable for removing, said indicating currents through filters that will exclude the main power supply current and segregate said currents, and means for recording the measurement made by the instrument as indicated by the said indicating currents.

7. In a device for geophysical exploration in which an instrument is lowered into an opening in the earth to Ameasure characteristics of the surrounding strata and a recorder is positioned at the surface to-record the measurements, the improvement which comprises as means to con nect the measuring instrument with the recorder and at least one source of power also positioned on the surface, a cable connected to the measuring instrument and extending to the surface tofsupport the measuring instrument and form an electrical connection thereto, a source of alternating electrical current connected to said cable and the ground at the upper end of the cable, means at the measuring device connected between the ground and the lower end of the cable for receiving said current and utilizing it as power to operate the measuring device, means at the measuring device for impressing upon the s urrounding earth and the supporting cable at least two alternating electrical currents of frey 8. a device forgeophysical exploration in' which an instrument comprising an ionization anda recorder is positioned atuthe'surface to' record the measurements, the improvement which comprises 'as'means to connect the measuring instrument with the recorder *and with a source of power, also positioned on the surface, a cable rconnected to the measuring instrument and extending ,to the surface toSupDOrt the measuring instrument and' form'v an electrical connection thereto, a source 'oi electrical 'current connected to said cable and the ground at `the uppersend of the'cable, 4means at the measuring device connected 'between the ground and the lower end of the cable for` receiving said current and converting it into power to operate the measuring device,`lincluding, primarily, a con-4 stant electrical potential for saidV ionization chamber circuit, means also at the upper end of the ycable for supplying axbalancin'g current to bring l,the 4measuring device to 1a stater'of balance during the measurement, said meansv being connected to the cable and ground at the upper end'of thecabl'e, means at theV measuring' instrulfrom said cable and ground and applying it to a balancing resistor connected at one end to the resistor in the ionization chamber circuit so that the voltage developed across the two resistors will be the difference between the voltages developed by the ionization chamber current in the primary resistor and that developed by the balancing cur. rent in the balancing resistor, commutator means driven by current from` the power supply means for generating a constant amplitude, constant frequency, alternating phasing current and at the same time converting any voltage diierence developed across the balancing and primary resisters into an alternating, indicating current of the same frequency as the phasing current but with an amplitude and phase relation to the phasing current that depends upon the magnitude and direction of said voltage difference,

means at the measuring device powered by said' power supply means for impressing upon the cable and ground one of said alternating currents, said means including a lterwhich excludes currents of other frequencies, lmeans powered by said power supply means for generating and impressing on the ground and cable a carrier current of -a different frequency from said alternating currents, but modulated by the other alternating current, said means including a iiln ter which excludes frequencies other than that of the carrier current, means at the surface end of the cable for removing and separating the phasing and indicating currents through filters that exclude the power supply current and other unwanted currents, means for comparing said phasing and indicating currents, means for adjusting the balancing current by reference to said comparison to bring the instrument to a state of balance and means to record the `amount of current necessary to establish balance.

,9, In a. device for geophysical explorationv which includes a measuring instrument adapted to belowered into a drill hole to measure phenomena indicative of the character of the sur-l rounding strata, a recorder on the surface for recording said measurements and a supporting Goble coni-rooted. to the, recorder soooorryins the instromers the, improvements which commise Ineens et the measuring; instniirierit for; serif. cretino electrical oscillations. Ineens for mode' latins tlie emolitiiiie ci seiososcillotions ses cordsrice with' tile fmseriituds of necessite-A nient beine mede, to generate oscillo-` tionsofy .e frequency oii'iererit from the first mentioned. oscillations ond` of. c, constorit. amplitodo, means to. onerosi both of scid oscillations upori` .the cable-:oost the surrounding earth-et. the measuring. instrument, means at the siiriiice` oi thev eorth to detect classify both of, seid. os-A oillctions, and moons for: recording at least one rif-said oscillstione.-y

10,. Method; of seooliysiesl exploration coni-` crisiiissuspe.iioliriis` e sensitire sienslsproduciiig instrument onoriL an electrically conductive sui?- vortice:- oeblei movies, the suspended, instrument.

within a wellI bore beliisf explored; creatine, at

1eosttwoe1ternatirig electrical currents of diff ferent frequencies inA the ostile,-sirici surrounding earth. the phase retentionr aride relative magnitude of oer-tenir; components o; saidL alternating currents; beine related to. signals produced by said instrumenta, reeeiviiicrthe curreritotromf the cable etA thesorfsce ofA trie` earth; segregctine: and' clescrosses i sii-Xios the comoorierit currents, and.. opcraetiiic recording means. controlled by said currents; to produce. e record ofthe signals. transmitted by the sensitive instrument.

11. In c device for geophysical exploration which includes a. measuring instrument adapted to be lowered into a drill hole to measure Dllef-A nomena indicative of the character of the surrounding strata, a recorder on the surface for recording said measurements and a supporting cable connected to the recorder and carrying the instrument, the improvements which comprise means .et the measuring instrument for gener,- ctiue electrical oscillations, means for rriodu.` latins. the amplitude of seid oscillations in socordsince with the magnitude ofY the measures merit beine mede, means to generate oscillations ot s frequency different from the first-mentioned osoilleitions,sind` of c constant amplitude, means for combining and transmitting loothof said oscilletions to the surace of the earth, means @t the surface of the earth to receive said combined oscillations, and means for actuating the recorder in accordance With the modulation of said rst generated oscillations,

ROBERT EARL FEARON. 

